Devices for producing a loop at the end of a coil spring are, as a rule, positioned before a leg spring machine, wherein the spring is prefabricated, i.e., wound or bent, whereby the prefabricated spring, before the cutting of the wire, is gripped by the grippers of a gripping unit of the device, is fed to a loop producing device after the cutting and the second loop produced at the end of the spring. The first loop at the beginning of the spring is already produced in the spring machine. However, in principle, such devices for affixing of a loop can be coupled with any kind of spring machine.
From DE 1 402 878 C, a device is known, whereby in several stations loops are produced on both ends of a spring. However, this known device is very elaborate and requires significant floor space. The individual devices contained therein are driven by a continuous pull of drive shafts arranged rectangularly to each other and coupled by means of bevel gear pairs, one of which is driven by an assigned spring winding machine. The great number of applied mechanical parts in connection with the complicated kinematics and the continuous mechanical control of all elements requires that relatively great power be applied for the operation of said device simply to overcome the notable friction, whereby efficiency as well as processing speed of said device are markedly limited.
In U.S. Pat. No. 3,782,425 A, a device for producing a loop at the end of a coil spring is described, whereby the coil spring is held in a processing position by a gripping unit with gripper jaws. Thereby, an upper end turn of the spring protrudes over the gripper jaws, which is gripped from underneath by a first tool with a beveled front edge approaching laterally and which is tilted upward to a certain height through a further approach of said tool. Subsequently, the tool is retracted and the end turn is moved still further in its exposed end position by means of a second tool approaching from the same side, whereby the upended spring turn is pressed against a third tool approaching from the opposite direction, acting as a type of stop. This known device operates in a relatively complicated manner and with a great number of individual steps, and allows for the execution of only one type of upward bending of the uppermost end turn of the spring.
Furthermore, another device is known (EP 0 117 097 B1) with which on coil springs that exhibit on their end a protruding tongue and the end of which exhibits a bent hook, the tongue, positioned tangentially to the end turn of the coil spring, is bent upward during the removal from the spring manufacturing machine in a direction parallel to the central axis of the spring. In this device, a gripping unit with gripper jaws for retaining the spring in a processing position with predetermined alignment of the central axis of the spring is provided, whereby the gripping unit can be moved to and also from the processing position. Thereby, the spring is positioned in the gripping unit in such a way that the contact tongue, positioned tangentially to the coil spring, with the already formed hook-shaped end bend protrudes sideways above the gripper jaws. For the tilting up of said tongue a tool is provided which is moved laterally in the direction of the spring and which exhibits on its upper side a beveled approach area, which approaches the protruding tongue at its free end from underneath and subsequently is tilted upward while entraining the tongue. At the same time, an additional tool is moved toward the spring from the opposite side, which exhibits a counter block with a bending edge as a bending form during the tilting up of the loop by the first tool. The approach of the second tool takes place in the processing position of the gripping unit in such a way that the counter block is moved via the uppermost end turn of the spring to a position at which the tongue is bent by the first tool. Thereby, the first tool consists of a tool bit, which is fastened to an angle lever. In order to swivel the tool bit, the angle lever grips, at its free lever end opposite of the tool bit, via a protruding roller into an assigned, inclined sliding-block track, which is designed as a rigid body. The angle lever sits on a mount, which is laterally movable, i.e., to and from the gripping unit, and the lateral movement of which is controlled via a cam gear.
Likewise, the approach and/or retraction of the second tool with the counter block is controlled, once again, by its own cam gear. Thereby, an additional third cam gear is provided, with which the spring can be removed from the processing position after the upward bending of the tongue. However, this known device is only suited for the upward tilting of a tongue of a coil spring protruding sideways over the gripper jaws but not for the forming of a loop for the upward tilting of an entire end turn or a part thereof, which does not protrude radially over the gripper jaws. In addition, due to the great number of applied cam gears, this known device is complicated with overall very complex kinematics, which in turn requires relatively great expenditure of energy for its operation, and the possible maximum processing speed is also not very high.
Therefore, it is the objective of the invention to provide a device which allows for the manufacture of half and whole German loops, English loops as well as hook loops on right-hand as well as left-hand spring bodies, whereby the loops can be pulled up from the spring body as well as bent up. In addition, the device should be designed relatively simply and allow for a high feed speed.